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observing with diagonal

mark81

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mark81

mark81

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hi all, so suddenly I'm getting all confused about using my diagonal. The image is the wrong way round right? Is it also upside down? I'm having real trouble locating objects when I know I'm so close to them and its making my brain hurt...

any advice or comments welcome....

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JeremyS

JeremyS

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31 minutes ago, mark81 said:

hi all, so suddenly I'm getting all confused about using my diagonal. The image is the wrong way round right? Is it also upside down? I'm having real trouble locating objects when I know I'm so close to them and its making my brain hurt...

any advice or comments welcome....

Have a look at this tutorial on the BAA website https://britastro.org/node/12707

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domstar

domstar

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Also, check the diagonal is pointing straight up. I used to bend mine round at an angle so I could be in a comfortable sitting position from the side. That's OK but it rotates everything and I was often confused. If it is pointed up as usual, then up and down are the same but left right is reversed as Gordon said. If you have a normal finder (don't know the name- not red dot or right angle), then the finder will be reversed and upside down, which confused me for a (long) time.

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NGC 1502

NGC 1502

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Posted

 

 One tip that I find useful is - whatever type of scope, whether or not you are using a diagonal and whatever angle it’s inserted in the focuser, is that stars always drift out of the field of view to the west, new stars enter the field of view from the east. That gets at least 2 directions sorted......and if your scope is driven, turn off the drive to see this happen.....then to find north, push the scope towards Polaris, new stars enter the field of view from the north. Obviously the other direction will be south.

Now you are sorted with directions, and if you are a manual star hopper, knowing which way is which will help greatly.

Unless of course you happen to be in the Southern Hemisphere.......

HTH, Ed.

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LukeSkywatcher

LukeSkywatcher

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I may buy myself one of those. The one i have is a cheapy. I think it came with my 70mm Celestron travelscope. Thinking about it, id buy a good 45 degree one because i observe from a seated position it would be more comfortable then stretching bending my neck to look into a 90 degree. 90 degree are fine is standing over your scope.

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Paz

Paz

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I'd also vote for getting a correct image diagonal. I've got a nice mirror diagonal that gives better images than my correct image diagonal, but despite this the correct image diagonal gets 90% of the action because I find flipped images to be really difficult to get on with.

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NGC 1502

NGC 1502

Posted
Posted
22 hours ago, Paz said:

I'd also vote for getting a correct image diagonal. I've got a nice mirror diagonal that gives better images than my correct image diagonal, but despite this the correct image diagonal gets 90% of the action because I find flipped images to be really difficult to get on with.

 

One of the members at my local club uses an 80mm birding scope for astronomy because he too prefers a “correct” view.

I can readily understand that. His scope has an adapter to take 1.25” fitting eyepieces in the 45 degree angled focuser. He is also a keen birdwatcher so his scope is doubly useful.

Ed.

 

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John

John

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Personally I'd rather get used to the image inversion than put something in the optical train that undermines the optical performance of the system, even if it's just a little. It's hard enough to see some of the more subtle targets as it is without adding to the challenge :dontknow:

Our eyes invert the view and then our brains reverse that so it's arguable what is the "correct" image anyway, especially when viewing objects in space :icon_scratch:

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John

John

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4 minutes ago, Doc said:

I use a APM erecting prism and it is the best thing I've bought, makes star hopping so much easier. 

I use such prisms in my finders for that purpose. Once I get to an eyepiece view the final finding, if needed, is done using charts that emulate the scope view. With newtonians (and it's that scope type that I do most of my more challenging object observing with) we are stuck with the inverted / reversed view so have to get used to it !

The APM erecting prism looks a nice item though :icon_biggrin:

http://www.apm-telescopes.de/en/optical-accessories/stardiagonal-mirror--prism/apm-2-inch-erect-image-prism-fast-lock-ultra-broadband-coating

 

 

 

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Ruud

Ruud

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I vote against an erecting prism. It degrades the image.

You got used to your image in the mirror. That's left-right reversed. You'll get used to the image in your diagonal.

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25585

25585

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25 minutes ago, John said:

Personally I'd rather get used to the image inversion than put something in the optical train that undermines the optical performance of the system, even if it's just a little. It's hard enough to see some of the more subtle targets as it is without adding to the challenge :dontknow:

Our eyes invert the view and then our brains reverse that so it's arguable what is the "correct" image anyway, especially when viewing objects in space :icon_scratch:

What is so confusing is moving from an atlas to eyepiece, whether Newtonian or diagonal.

Going from normal to finder scope (refractor with or without diagonal) then to a Newtonian in quick succession can make a person feel giddy as a guide star & target are differently oriented for each.

My Sarna atlas has Newtonian south-on-top charts, but I don't know any others with through-the-eyepiece plotting. I guess a right-way-up page could be scanned & oriented for a diagonal etc, then printed.

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John

John

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1 minute ago, 25585 said:

Going from normal to finder scope (refractor with or without diagonal) then to a Newtonian in quick succession can make a person feel giddy as a guide star & target are differently oriented for each....

 

I don't find this. I move frequently between a star chart - Rigel Quickfinder - 9x50 RACI optical finder - eyepiece in a newtonian and don't feel queasy at all. Sometimes chillly, occasionally frustrated and every now and then excited but as yet, not giddy or queasy.

I'm going to have to have a sick bag on standby in future though, just in case ! :icon_puke_r::smiley:

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iPeace

iPeace

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Posted

If you consider a telescope as a way of 'getting closer' to something you'd like to see, then - to my feeble mind - an image which is flipped left-to-right doesn't represent what you'd see if you could actually get that close (in your space ship).

The newtonian (or 'straight through' with a refractor etc.) view, which (if I've seen correctly, getting older :confused4:) is not flipped but rotated, does represent what you'd actually see; you'd merely be flying your space ship 'inverted' (up side down), something you'd not notice in space...

A correct-image diagonal (I'm assuming a frac, mak, etc.) represents the exact same view your naked eyes have from your particular spot on planet Earth, only closer. Sounds ideal, and works intuitively, certainly with many of the available charts, maps, etc.

However...the correct-image diagonal can indeed degrade the image relative to that presented by a mirror diagonal. So some things may not be seen at all. These things would arguably be difficult to see even with the mirror diagonal, but there will always be those difficult-to-spot objects that you can (just) see with the mirror diagonal but not with the correct-image diagonal. Whether this matters to you, and if so, how much, is entirely a matter of preference.

So - pick your poison. :icon_biggrin: Or don't - just get both. Use a correct-image and a mirror diagonal side-by-side, saving the mirror diagonal to squeeze out that last bit of image in order to see that faint, tight companion star you otherwise wouldn't see. Or use either depending on how you feel on the night.

I have and use both types of diagonal, and enjoy using both, as well as the newt view. I do enjoy star-hopping and lunar observation more with a correct-image diagonal than with a mirror diagonal.

I must agree though - if you can only have one (either mirror or correct-image) diagonal, and you want the best possible image (all things being equal), getting used to the 'left-right-flipped' view is the way to go.

Then again, no matter what you use, there will always be objects out of reach. So make sure you have what you enjoy using most.

:happy11:

 

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LukeSkywatcher

LukeSkywatcher

Posted
Posted
1 hour ago, John said:

Personally I'd rather get used to the image inversion than put something in the optical train that undermines the optical performance of the system, even if it's just a little. It's hard enough to see some of the more subtle targets as it is without adding to the challenge :dontknow:

Our eyes invert the view and then our brains reverse that so it's arguable what is the "correct" image anyway, especially when viewing objects in space :icon_scratch:

All fair and valid points. I guess im just stuck in my ways. Ever since ive been observing with binoculars or telescopes, everything has always been in the "correct orientation". I guess ive never bought a scope that uses a star diagonal (which would be strange), or ive gotten one but immediately put it to one side in favour of an erect prism which i received with one of my scopes. Honestly cant remember which scope came with erect prism. Could have been my 1st scope Celestron 90EQ?, or perhaps the travelscope 70 which i bought very soon after the 90EQ. The 90EQ really never got more then about 3 outings before i bought the 70mm. The period between these 2 scopes was filled by me buying my 20x90 bins. 

 

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25585

25585

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4 hours ago, LukeSkywatcher said:

I've been eyeing this one on and off for about a year. Any thoughts?. I've never bought any WO before. 

https://www.firstlightoptics.com/diagonals/william-optics-125-45-degree-erect

I have a couple of these https://www.firstlightoptics.com/diagonals/william-optics-125-90-degree-erecting-prism.html

Cheaper and with their own helical focuser

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Doc

Doc

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1 hour ago, Ruud said:

I vote against an erecting prism. It degrades the image.

You got used to your image in the mirror. That's left-right reversed. You'll get used to the image in your diagonal.

Have you used the APM or Zeiss models Ruud? 

I cannot see no degrading at all.

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